Choe et al showed that rates of antibody positivity was still high after 8 months, however, neutralizing activity was only detected in 53.4% of asymptomatic or mildly symptomatic participants after 8 months of infection,

Crawford et al: Neutralizing antibody titres (and total antibodies) declined an average of about 4-fold from 1 to 4 months after symptom onset.

Choe PG, Kim KH, Kang CK, et al. Antibody Responses 8 Months after Asymptomatic or Mild SARS-CoV-2 Infection. Emerg Infect Dis. 2021;27(3):928-931. doi:10.3201/eid2703.204543

Katharine H D Crawford, Adam S Dingens, Rachel Eguia, Caitlin R Wolf, Naomi Wilcox, Jennifer K Logue, Kiel Shuey, Amanda M Casto, Brooke Fiala, Samuel Wrenn, Deleah Pettie, Neil P King, Alexander L Greninger, Helen Y Chu, Jesse D Bloom, Dynamics of Neutralizing Antibody Titers in the Months After Severe Acute Respiratory Syndrome Coronavirus 2 Infection, The Journal of Infectious Diseases, Volume 223, Issue 2, 15 January 2021, Pages 197–205, https://doi.org/10.1093/infdis/jiaa618